Preheat oven to 350° F (temperature can be 25 degrees higher or lower, if needed, to accommodate other food being cooked).

Prepare the garlic by removing most of the outer papery layers, leaving enough to keep the heads intact. Trim off any roots, and slice off the top 1/4 to 1/3 of the head, to expose the tops of the individual cloves.

Arrange in suitable baking dish. Salt lightly and drizzle olive oil over the exposed tops. Add water to come about 1/4" up the sides of the heads. Cover with aluminum foil and bake in preheated oven until cloves are very soft, about 1 hour.